This application claims the benefit of Japanese Application No. 10-309972 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a shock absorbing type steering apparatus and a structure for mounting to an automobile body the same steering apparatus and, more particularly, to a technology of smoothing collapses of a steering shaft and a steering column upon a collision.
2. Related Background Art
In the event of a collision of an automobile with another automobile or some sort of structure, a driver might secondarily collide against a steering wheel, with the result that the head and/or sternum would be seriously injured.
The automobiles manufactured over the recent years have broadly adopted a shock absorbing type steering apparatus in order to prevent such an injury. The shock absorbing type steering apparatus is structured so that the steering shaft on the side of the steering wheel collapses (shrinks in length) upon the secondary collision of the driver, wherein the steering shaft is separated into an outer shaft and an inner shaft which are slidably joined at mating serrated portions. Further, in the great majority of shock absorbing type steering apparatuses, the steering column is also separated into an outer column and an inner column which are slidably joined.
Normally, an impact energy absorbing mechanism (such as a slide resistance of the serrated portions meshing with each other) for resisting the collapse, is provided between the outer shaft and the inner shaft. The steering shaft, when an axial load exceeding a predetermined value acts thereon, collapses, and on this occasion an impact energy is absorbed by the impact energy absorbing mechanism. Note that in general an upper portion of the steering column comes off a car body structural member upon the secondary collision of the driver in order to make the steering upper shaft collapsible.
In addition, the steering apparatus of the automobile is operated (steered) by an unspecified multiplicity of drivers, and it is therefore desirable that a position of the steering wheel be adjustable corresponding to an individual physique and a driving posture. For meeting such a demand, not only the automobiles but also trucks adopt a large variety of tilt steering apparatuses each having a tilt mechanism. The tilt mechanism is a mechanism for adjusting the position of the steering wheel in an up-and-down direction, and is constructed of a tilt pivot serving as a center of rocking movement of the steering shaft and of the steering column, and a tilt adjusting mechanism for fixing the steering column in a desired position (at a desired angle).
The shock absorbing type steering apparatus having the tilt mechanism has a drawback in that the impact energy is not smoothly absorbed due to the rocking movement of the steering column when the secondary collision happens. For example, when the driver collides against the steering wheel, the steering column, after coming off a car body structural member such as a cross member, makes rocking movement about the tilt pivot. On this occasion, if the steering column largely moves upwards, a bending moment acts on the steering shaft and on the steering column pressed against the driver""s body moving forwards, with the result that the steering upper shaft is more or less bent.
As a result, entry of the inner shaft into the outer column is impeded, and the steering upper shaft does not smoothly collapse. Then, it follows that an impact energy absorbing performance declines. Especially in an apparatus wherein the steering column is provided with a power assist mechanism constructed of an electric motor and a gear box etc, the bending moment caused in the steering column is increased by an inertia etc of the power assist mechanism, with the result that the shaft becomes much harder to collapse.
It is a primary object of the present invention, which was contrived to remedy the foregoing difficulties, to provide a shock absorbing type steering apparatus and a structure for mounting to an automobile body the same steering apparatus capable of attaining a smooth collapse of a steering shaft by regulating an upward movement of a steering column.
To accomplish the above object, according to a first aspect of the present invention, a shock absorbing type steering apparatus comprises a steering upper shaft, of which a rear side end is fitted with a steering wheel, provided with a collapsible mechanism, a steering column for rotatably supporting the steering upper shaft therein, a first column bracket formed on the side of a front side end of the steering column and used for fixing a front portion of the steering column to a car body structural member, a second column bracket, formed on the side of a rear side end of the steering column and used for fixing a rear portion of the steering column to the car body structural member, for permitting the rear portion of the steering column to be released forward from the car body structural member, and a collapsible mechanism provided between the first column bracket and the second column bracket in the steering column and operating with the collapsing motion of the steering upper shaft. A guide plate with which an upper surface of the steering column comes into contact, is fixedly fitted to the fixed bracket in order to regulate an upward movement of the steering column when the movable bracket is released from the fixed bracket by dint of an impact force on the steering wheel and when a rear portion of the steering column moves forward.
In the shock absorbing type steering apparatus according to the first aspect of the invention, even if an upward spring force acts on the steering wheel upon a secondary collision of a driver, the guide plate regulates an upward movement of the steering column, whereby there are almost no flexures or bends of the steering shaft and of the steering column, and the collapses of the steering shaft and the steering column are smoothed.
According to a second aspect of the present invention, in the shock absorbing type steering apparatus according to the first aspect, at least a contact portion of the guide plate with the steering column is composed of a low-friction material.
In this shock absorbing type steering apparatus according to the second aspect, a frictional resistance between the guide plate and the steering column decreases, and hence the steering column collapses more smoothly.
According to a third aspect of the present invention, in the shock absorbing type steering apparatus according to the first or second aspect, the steering column has a tilt mechanism, and the steering column comes into contact with the guide plate at an upper limit of a tilt adjusting range.
In the shock absorbing type steering apparatus according to the third aspect, the guide plate serves as a stopper when the steering column moves up to an upper limit of tilt adjustment, and, if the guide plate is composed of an elastic material, there is prevented a striking sound emitted when the guide plate impinges upon the steering column.
According to a fourth aspect of the present invention, there is provided a structure for mounting to an automobile body a shock absorbing type steering apparatus comprising a steering upper shaft, of which a rear side end is fitted with a steering wheel, provided with a collapsible mechanism, a steering column for rotatably supporting the steering upper shaft therein, the structure comprising a first column bracket formed on the side of a front side end of the steering column and used for fixing a front portion of the steering column to the automobile body structural member, a second column bracket, formed on the side of a rear side end of the steering column and used for fixing a rear portion of the steering column to the automobile body structural member, for permitting the rear portion of the steering column to be released forward from the automobile body structural member, and a collapsible mechanism provided between the first column bracket and the second column bracket in the steering column and operating with the collapsing motion of the steering upper shaft, wherein a guide plate with which an upper surface of the steering column comes into contact, is fixedly fitted to the automobile body structural member in order to regulate an upward movement of the steering column when the movable bracket is released from the fixed bracket by dint of an impact force on the steering wheel and when a rear portion of the steering column moves forward.
In the mounting structure according to the fourth aspect, even if the upward spring force acts on the steering wheel upon the secondary collision of the driver, the guide plate regulates the upward movement of the steering column, whereby there are almost no flexures or bends of the steering shaft and of the steering column, and the collapses of the steering shaft and the steering column are smoothed.
According to a fifth aspect of the present invention, in the mounting structure according to the fourth aspect, at least a contact portion of the guide plate with the steering column is composed of a low-friction material.
In the mounting structure according to the fifth aspect, the frictional resistance between the guide plate and the steering column decreases, and hence the steering column collapses more smoothly.
According to a sixth aspect of the present invention, in the mounting structure according to the fourth or fifth aspect, the steering column has a tilt mechanism, and the steering column comes into contact with the guide plate at an upper limit of a tilt adjusting range.
In the mounting structure according to the sixth aspect, the guide plate serves as the stopper when the steering column moves up to an upper limit of the tilt adjustment, and, if the guide plate is composed of the elastic material, there is prevented the striking sound emitted when the guide plate impinges upon the steering column.